Sand consolidation method



United States Patent Delaware No Drawing. Filed Sept. 8, 1958, Ser. No. 759,441

- 3 Claims. (Cl. 166-33) This invention is directed to a method for consolidating loose or incompetent formations penetrated by a borehole.

More particularly, this invention is directed to a method for consolidating the sands. of subsurface formations by injection of fluids into the formations.

in producing fluids from subsurface formations sand is produced along with the formation fluids from loosely consolidated formations. Because production of sand with its attendant accumulation in the well bore or movement to the surface is undesired, various sand control measures have been used to inhibit or prevent sand particles from moving into the well bore. One sand control measure is the use of porous setting plastics which bind the sand particles together while permitting flow of well fluids therethrough. A desired characteristic of such plastics is the ability to wet sand grains.

Particularly good consolidating plastics of this type make use of the resin-forming properties of the reaction between a water soluble aldehyde and a low molecular weight hydroxy aryl compound catalyzed by an alkaline or acidic catalyst. When these compounds are injected into a sand formation, a resin forms which cements the particles of the formation together. Although any water soluble aldehyde may be used formaldehyde, acetaldehyde, propionaldehyde, or mixtures thereof are preferred. The low molecular weight hydroxy aryl compound may include phenol, cresol, beta naphthol, resorcinol, or cresylic acid, or mixtures thereof. Suitable alkaline catalysts which may be used include guanidine salts such as guanidine carbonate and amino-guanidine bicarbonate; alkali metal hydroxides and carbonates such as sodium hydroxide or sodium carbonate; aliphatic amines such as ethyl amine and triethyl amine; aromatic amines such as analine; and aliphatic diamines such as' ethylene-diamine. Suitable acidic catalysts which may be used include acidic salts such as stannous chloride or magnesium chloride; mineral acids such as hydrochloric acid or sulfuric acid; acid anhydrides such as maleic anhydrides; aromatic acids such as picric acid or benzene sulfonic acid or sulfanilic acid; and polynuclear aromatic acids or acid salts such as alpha nahpthylamine sulfonic acid or sodium-l-naphthylamine-3,6,S trisulfonate.

A method of sand consolidation employing a plastic of the type utilizing an acidic catalyst is disadvantageous in that it cannot be used successfully on calcareous sands containing .5 or more carbonate. Additionally, two or more stages of plastic treatment are required even on sands containing negligible amounts of carbonate. A multiple stage process is disadvantageous in that it is time consuming and costly because of the necessary waiting time of several hours between stages; also, twice as much plastic must be used in the multiple stage process as is needed in a one stage process.

A method of sand consolidation employing a plastic of the type utilizing an alkaline catalyst can be used successfully to consolidate the sands of calcareous and noncalcareous formations. However, two or more stages of plastic treatment may be required to consolidate these I sands.

Resin-forming compositions employed for consolidating sands in oil producing formations are only slightly miscible with either oil or water. Fluid flow studies show 3,047,067 Patented July 31, 1962 ice that in order for one liquid to efficiently displace another liquid from the surface of a sand grain, the two liquids should be mutually miscible. Since one desired requisite for successful sand consolidation with a plastic mixture is that the sand grains be wetted by the plastic, the liquid in contact with the sand grains should be replaced prior to the injection of the consolidating plastic by another liquid with which the plastic mixture is miscible.

in the case of water-wet sands, the formation may be pretreated by replacing the water normally in contact with the sand grains with another liquid with which the plastic is miscible prior to injection of the resin-forming mixture in order'to achieve a single stage consolidation with an a kaline catalyzed resin-forming mixture.

Thus, by injecting a polar organic compound miscible with both the connate Water and the plastic solution into the formation to displace the connate water prior to injection of the plastic solution, an alkaline catalyzed plastic can successfully consolidate field sands including those containing as much as 10% carbonate; furthermore, the sand consolidation is accomplished successfully with the injection of a single stage of the resin-forming mixture and the resulting consolidated formation retains about 60% of its original permeability. Formalin, methanol, acetone, methylamine, or other alcohol, ketone or solution of aldehydes or amines are examples of polar organic compounds that may be used in this pretreatment to displace the connate water and to be displaced by the plastic solution. This method of sand consolidation is disclosed and claimed in U.S. application Serial No. 759,442, entitled Method for Consolidation of Sand by R. E. Williams et al., filed September 8, 1958.

The method of the present invention particularly concerns the case of oil-wet sand in which the polar organic compound does not displace the oil from the sand surface and comprises adding a surface active agent to the pretreating polar organic compound. However, the method of the invention may be employed advantageously in the consolidation of predominantly Water-Wet sands or mixed wettability sands. The latter sands are sands having areas of water-wetness and areas of oil-wetness. The surface active agent has the property of being adsorbed on the sand surface thereby displacing the oil and rendering the surface wet by the polar organic compound which is subsequently displaced by the plastic mixture. Addition of the surface active agent to the polar organic compound permits a single stage consolidation to be achieved with either an acidic or an alkaline catalyzed resin-forming mixture.

The surface active agents suitable for inclusion in the polar organic compound to render sand surfaces plastic wet may be anionic agents such as alkyl, aryl, or alkyl aryl sulfonates :or sulfates, sulfated or sulfonated amides, others or esters; cationic agents such as amine salts or quaternary ammonium chlorides; or non-ionic agents such as esters, ethers, or etheresters of the natural fats and oils; or the alkyl phenols. Polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate, oxyalkylated amylphenol, alkyl aryl polyether alcohol, and polyoxyethylene ether are examples of surface active agents which have been used.

In order to insure that no plastic is left in the well.

bore and to increase the permeability of the consolidated formation, it is desirable tooverfiush the formation; that j is, displace the plastic treating liquids into the formation 1 with oil. However, when oil is displaced into the forma tion, the effectiveness of the consolidation treatment is in order to prevent the formation and the well from producing sand. Addition of a low molecular weight hydroxy aryl compound to the overflushing oil prevents extraction of the oil soluble compound from the resin-forming mixture and allows the formation immediately adjacent the well bore to be consolidated. Additionally, it permits the total volume of the formation treated to have a greater strength than could be obtained if a hydroxy aryl compound was not added to the displacing oil. This method for improving plastic sand consolidation is disclosed and claimed in U.S. patent application Serial No. 759,511, entitled, An Improved Method for Sand Consolidation, filed September 8, 1958, by Winsauer et al.

In one aspect thereof the present invention is to be considered as encompassing the combined pretreatment and overfiushing methods.

One object of the inventionis to provide methods of sand consolidation that are cheap, quick acting, and generally applicable to various types of formations. 7

Thus to successfully consolidate field sands, the subsurface formation is first flushed with a polar organic compound to which has'been added a surface active agent. Then a resin-forming mixture including a water soluble aldehyde and a low molecular weight hydroxy aryl compound catalyzed by either an acidic or alkaline catalyst is injected into the pretreated formation. The exact resinforming composition will depend upon the well temperature. The resin-forming mixture displaces the polar organic compound by miscible displacement. The resin then is allowed to remain in the formation until it is hard. The timerequired for hardening is between 8 and 24 hours depending upon the well temperature. If desired, following the injection of the resin-forming mixture, the formation may be overfiushed by injecting a mixture of oil and a low molecular weight hydroxy aryl compound into the formation.

The practice of the invention is illustrated by the following experimental procedure:

Sand was packed in a 1 /2 inch diameter glass column equipped with heads and suitable connections to permit fluid to flow through the column and the glass column was placed in a 130 F. water bath.

The following series of experiments were conducted employing as the plastic solution formalin, cresol in the ratio of 4:1, guanidine carbonate in the range of 5 to of the weight of the formalin, cresol mixture, and sodium hydroxide in the range of 2 to 3% by weight of the formalin, cresol mixture. 7 7

Experiment I.--A predominantly water wet sand from the Miocene formation was treated with a single stage of the plastic solution. After curing the sand was found to be essentially unconsolidated. Cores drilled from the sand had compressive strengths of less than 40 lbs. per square inch.

Experiment H.A'sample of the same kind of sand treated in Experiment I was flushed first with a polar organic compound (a 37% solutionof formaldehyde) and, thenitreated with a single stage of the plastic solut ou. The following permeability and compressive strength data were obtained:

Thusfa water wetj sand which could not be consolidated with the plastic solution was successfully consolidated by first treating the sand with a polar organic compound.

Experiment III.-A predominantly oil-wet sand from the McElroy formation in the Labbe field was flushed first vnith the polar organic compound and then with a single stage of the plastic solution. The cores were found to be essentially unconsolidated with compressive strengths of less than 40 lbs. per square inch after curing. 7

Experiment I V.-A sample of the same kind of sand treated in Experiment III was flushed first with the polar organic compound containing -a surface-active agent (an alkyl aryl polyether alcohol) and then treated with a single stage of the plastic solution. Cores obtained from this sand after curing had compressive strengths in excess of 400 lbs. per square inch and as high as 900 lbs. per square inch. The permeability of these cores were all in excess of 4.0 darcies. V

Thus, an oil-wet sand which could not be consolidated by preflushing with a polar organic compound was successfully consolidated by prefiushing with a polar organic compound containing a surface-active agent.

Another series of experiments which follow were conducted employing as the plastic solutions phenol formaldehyde in a ratio of 1:2 and 1:4 and stannous chloride in the range of 6 to 8% by weight of the phenol formaldehyde mixture. In these experiments the sands were first saturated with salt water and then flushed with diesel oil to simulate an oil sand with connate water.

Experiment V.-A sand from the Friendswood field was treated first with 150 ccs. of hydrochloric acid and then flushed with formalin. .The formalin was removed with diesel oil and the sand was treated with 75 ccs. of the plastic solution. Additionally, the sand was overfiushed with 150 ccs. of diesel oil containing 5% cresol. After curing, the sand was not consolidated.

Experiment VI.This experiment was similar to Experiment'V except the treatment with hydrochloric acid was omitted and the formalin used in the preflush contained 10% stannous chloride. After curing, the sand was not consolidated.

Another experiment which was conducted follows:

Experiment VII.A sand'of Experiments V and VI was preflushed with 10% stannous chloride in formalin containing 2% of a surface-active agent (an alkyl aryl polyether alcohol) and then treated with a consolidation solution composed of 2 parts formalin and 1 part of a phenol fraction composed of 75% phenol and 25% cresol and containing 6% by weight stannous chloride catalyst. After curing at212 F. the treated sand was found'to have an average permeability of 1.5 darcies and an average compressive strength of 820 p.s.i.

Thus, these experiments show that an acidic catalyzed plastic solution can successfully consolidate sands in one stage when the sands are first prefiushed with a polar organic compound containing a surface-active agent.

Having fully described the method and objects of the o invention, we claim:

,1. A method for consolidating the sands of an incompetent subsurface formation containing oil and connate liquids comprising pretreating the formation prior to introduction into the formation of liquids capable of forming a resin by introducing into the formation a liquid mixture of a surface-active agent and a polar organic coinpound miscible with both the resin-forming liquids and the connate liquids in the formation so as to remove the connate liquids and wet the sands with the polar organic compound; and then introducing into saidformation said resin-forming liquids which set inthe' formation and bind the sand. particles of the formation together, said resinforming liquids comprising-a low molecular weight hydroxy aryl compound, a water soluble aldehyde and a catalyst. V V

2. A. method as recited in claim 1 including employing an alkyl aryl polyether alcohol as said surface active agent.

References Cited in the file of this patent UNITED STATES PATENTS Moore et a]. Apr. 4, 1944 6 Wrightsman et al June 19, 1945 Wrightsman July 12, 1949 Wrightsman July 22, 1952 Maly Mar. 26, 1957 Vogel June 25, 1957 Garst July 30, 1957' 

1. A METHOD FOR CONSOLIDATING THE SANDS OF AN INCOMPETENT SUBSURFACE FORMATION CONTAINING OIL AND CONNATE LIQUIDS COMPRISING PRETREATING THE FORMATION PRIOR TO INTRODUCTION INTO THE FORMATION OF LIQUIDS CAPABLE OF FORMING A RESIN BY INTRODUCING INTO THE FORMATION A LIQUID MIXTURE OF A SURFACE-ACTIVE AGENT AND A POLAR ORGANIC COMPOUND MISCIBLE WITH BOTH THE RESIN-FORMING LIQUIDS AND THE CONNATE LIQUIDS IN THE FORMATION SO AS TO REMOVE THE CONNATE LIQUIDS AND WET THE SANDS WITH THE POLAR ORGANIC COMPOUND; AND THEN INTRODUCING INTO SAID FORMATION SAID RESIN-FORMING LIQUIDS WHICH SET IN THE FORMATION AND BIND THE SAND PARTICLES OF THE FORMATION TOGETHER, SAID RESINFORMING LIQUIDS COMPRISING A LOW MOLECULAR WEIGHT HYDROXY ARYL COMPOUND, A WATER SOLUBLE ALDEHYDE AND A CATALYST. 